#include <vector>
#include <stack>
using namespace std;
/*
 * @lc app=leetcode.cn id=341 lang=cpp
 *
 * [341] 扁平化嵌套列表迭代器
 */


// This is the interface that allows for creating nested lists.
// You should not implement it, or speculate about its implementation
class NestedInteger {
  public:
    // Return true if this NestedInteger holds a single integer, rather than a nested list.
    bool isInteger() const;
    // Return the single integer that this NestedInteger holds, if it holds a single integer
    // The result is undefined if this NestedInteger holds a nested list
    int getInteger() const;
    // Return the nested list that this NestedInteger holds, if it holds a nested list
    // The result is undefined if this NestedInteger holds a single integer
    const vector<NestedInteger> &getList() const;
};


// @lc code=start
/**
 * // This is the interface that allows for creating nested lists.
 * // You should not implement it, or speculate about its implementation
 * class NestedInteger {
 *   public:
 *     // Return true if this NestedInteger holds a single integer, rather than a nested list.
 *     bool isInteger() const;
 *
 *     // Return the single integer that this NestedInteger holds, if it holds a single integer
 *     // The result is undefined if this NestedInteger holds a nested list
 *     int getInteger() const;
 *
 *     // Return the nested list that this NestedInteger holds, if it holds a nested list
 *     // The result is undefined if this NestedInteger holds a single integer
 *     const vector<NestedInteger> &getList() const;
 * };
 */

class NestedIterator {
public:
    stack<NestedInteger> recursive;
    NestedIterator(vector<NestedInteger> &nestedList) {
        for (int i = nestedList.size() - 1; i >= 0; i--) recursive.push(nestedList[i]);    
    }
    
    int next() {
        NestedInteger ni = recursive.top();
        recursive.pop();
        return ni.getInteger();
    }
    
    bool hasNext() {
        while (!recursive.empty()) {
            NestedInteger ni = recursive.top();
            if (ni.isInteger()) return true;
            else {
                recursive.pop();
                vector<NestedInteger> _nl = ni.getList();
                for (int i = _nl.size() - 1; i >= 0; i--) recursive.push(_nl[i]);
            }
        }
        return false;
    }
};

/**
 * Your NestedIterator object will be instantiated and called as such:
 * NestedIterator i(nestedList);
 * while (i.hasNext()) cout << i.next();
 */
// @lc code=end

